Paronychia is an inflammation involving the lateral and proximal fingernail folds. Predisposing factors include overzealous manicuring, nail biting, thumbsucking, diabetes mellitus, and occupations in which the hands are frequently immersed in water [1]. Paronychia has also been reported in association with antiretroviral therapy for HIV infection [2,3], and with use of epidermal growth factor inhibitors [4].

Paronychia may be either acute or chronic.

●Acute paronychia is characterized by the onset of pain and erythema of the posterior or lateral nail folds, with subsequent development of a superficial abscess (picture 1A-C).

In digits without exposure to oral flora, acute paronychia is most commonly caused by skin flora (such as Staphylococcus aureus and Streptococcus pyogenes) [5].

In digits exposed to oral flora, acute paronychia may be caused by either skin or oral flora. In this setting, organisms include both aerobic bacteria (such as streptococci, S. aureus, and Eikenella corrodens) and anaerobic bacteria (such as Fusobacterium, Peptostreptococcus, Prevotella, and Porphyromonas spp) [6,7].

●Candida is frequently isolated from the proximal nail fold of patients with chronic paronychia (picture 2A-B) [8,9]. However, it is not clear that Candida infection is actually responsible for the onset and maintenance of the disease. On the other hand, there is substantial evidence that chronic paronychia represents an eczematous condition with a multifactorial etiology (see below) [10-13]. Acute bacterial paronychia can exacerbate the chronic swelling and erythema of the proximal nail fold associated with chronic paronychia.

Diagnosis — The clinical appearance of swollen, tender posterior or lateral nail folds should confirm the diagnosis of paronychia. A purulent fluid collection is often present in acute paronychia (picture 1A-C). Retraction of the proximal nail fold, loss of the cuticle, and nail dystrophy are common features of chronic paronychia (picture 2A-B).

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